pgsql: Fix another problem in SQL-MED \d displays: should have a clean

Log Message:
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Fix another problem in SQL-MED \d displays: should have a clean failure
report if the command is attempted against an old server.

Modified Files:
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pgsql/src/bin/psql:
describe.c (r1.191 -> r1.192)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/describe.c?r1=1.191&r2=1.192)